The White House on Wednesday voiced hope the upcoming summit between North Korea's Kim Jong Un and US President Donald Trump will proceed as planned, as Pyongyang threatened to pull out over US pressure for ‘unilateral nuclear abandonment.’

The comments from the North about the meeting, set for June 12 in Singapore, were the first sign of a hiccup after weeks of tentative rapprochement.

‘We're still hopeful that the meeting will take place and we'll continue down that path,’ White House Press Secretary Sarah Sanders told Fox News. ‘At the same time ... we've been prepared that these might be tough negotiations.’

‘The president is ready if the meeting takes place. And if it doesn't, we will continue the maximum pressure campaign that has been ongoing.’

In an angrily worded statement, the North warned on Wednesday it may back out of the high-level summit if the United States pressures it to give up its nuclear arsenal.

‘If the US is trying to drive us into a corner to force our unilateral nuclear abandonment, we will no longer be interested in such dialogue,’ first vice foreign minister Kim Kye Gwan said in a statement carried by state media.

In that case, he added, Pyongyang would have to ‘reconsider’ its participation at next month's summit in Singapore.

The first vice foreign minister also tore into Trump's National Security Advisor John Bolton for drawing parallels between North Korea and Libya, calling the comparison ‘absolutely absurd.’

‘We shed light on the quality of Bolton already in the past, and we do not hide our feeling of repugnance towards him,’ he said.

Bolton has pushed the idea of a deal with North Korea like that reached with Libya's Moamer Kadhafi, who agreed in 2003 to the elimination of his country's nuclear program and chemical weapons arsenal to gain sanctions relief.

After giving up his atomic program, Kadhafi was killed in 2011 in an uprising backed by NATO bombing.

- A plea from China -

Washington is pressing for North Korea's complete, verifiable and irreversible denuclearization. But so far, the North has given no public indication of what it is offering, beyond a broad commitment to denuclearization of the ‘Korean peninsula.’

Pyongyang ‘made clear on several occasions that precondition for denuclearization is to put an end to anti-DPRK hostile policy and nuclear threats and blackmail of the United States,’ the North Korean minister said.

In the past, Pyongyang has demanded the withdrawal of US troops stationed in the South, and an end to Washington's nuclear umbrella over its ally.

China, North Korea's sole major ally, called for the summit to go ahead.

Minister Kim also dismissed offers by US Secretary of State Mike Pompeo for US economic aid if the North denuclearizes.

‘We have never had any expectation of US support in carrying out our economic construction and will not at all make such a deal in future,’ he said.

- Tightrope diplomacy -

The North Korean warning follows a weeks-long charm offensive that has seen Kim Jong Un hold a historic summit with the South's president and meet twice with Chinese President Xi Jinping.

Pyongyang also raised hopes ahead of the US summit by announcing it will destroy its nuclear testing site next week.

Analysts said Pyongyang appeared to be trying to redefine the terms of the debate.

‘It's a diplomatic tactic,’ Kim Hyun-wook, professor at the Korea National Diplomatic Academy, told AFP, calling it ‘brinkmanship to change the US position.’

‘It looks like Kim Jong Un was pushed into accepting US demands for 'denuclearization-first' but is now trying to change its position after normalizing North Korea-China relations and securing economic assistance,’ he added.

‘The classic North Korean tightrope diplomacy between the US and China has begun.’

US officials have repeatedly claimed credit for Washington's ‘maximum pressure’ policy for bringing Pyongyang to the negotiating table.

Joshua Pollack of the Middlebury Institute for International Studies said Pyongyang had been irritated by the ‘triumphalist tone.’

‘The North Koreans aren't happy with what they're seeing and hearing,’ he said. ‘There is still a yawning gulf between expectations for diplomacy in Pyongyang and Washington, DC.’

- Thunderstruck -

KCNA also denounced the Max Thunder joint military exercises being held between the US and South Korea as a ‘rude and wicked provocation,’ and Seoul said it had received a message cancelling planned high-level talks ‘indefinitely.’

The two-week drills started last Friday and involves some 100 aircraft from the two allies, including F-22 stealth fighter jets.

State Department spokeswoman Heather Nauert told reporters it had received ‘no notification’ of a position change by North Korea on next month's meeting.